Intermediates for the production of quinolone carboxylic acid derivatives

ABSTRACT

Chemical intermediates which are of use in the production of quinolone carboxylic acid derivatives having antibacterial activity.

The present invention relates to novel compounds which are of use in theproduction of pharmaceutically active compounds, for example, quinolonecarboxylic acid derivatives having antibacterial activity.

EP 688772 discloses novel naphthyridine carboxylic acid derivativeshaving antibacterial activity, including anhydrous(R,S)7-(3-aminomethyl-4-methoxyiminopyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicacid of the formula:

WO 98/42705 discloses(R,S)-7-(3-aminomethyl-4-syn-methoxyimino-pyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicacid methanesulfonate and hydrates thereof including the sesquihydrate.

PCT/KR99/00099 (published after the priority date of the presentapplication) discloses a process for the production of4-aminomethyl-3-alkoxyiminopyrrolidines and salts thereof fromaminomethylpyrrolidin-3-one and the corresponding alkoxylamine. Suitablesalts of the 4-aminomethyl-3-alkoxyiminopyrrolidines are described asthe hydrochloride, trifluoroacetate and sulfate salts.

The present invention relates to novel4-aminomethyl-3-alkoxyiminopyrrolidine salts which are of use in thesynthesis of pharmaceutically active compounds.

According to the invention there is provided a compound of formula (I):

-   -   wherein R is C₁₋₄ alkyl or C₁₋₄ haloalkyl.

The compound of formula (I) is preferably4-aminomethyl-3-methoxyiminopyrrolidinium dimethanesulfonate.

According to a further aspect of the invention there is provided aprocess for the production of a compound of formula (I) which comprisesreaction of a compound of formula (II):

-   -   wherein R is as defined for formula (I) and P₁ and P₂, which may        be the same or different, are amino protecting groups, with        methanesulfonic acid.

Suitable protecting groups P₁ and P₂ include any suitable aminoprotecting groups which are removable by treatment with methanesulfonicacid. The preferred protecting group for both P₁ and P₂ ist-butoxycarbonyl.

The reaction of the compound of formula (II) and methanesulfonic acid issuitably carried out at a temperature between about 10° C. and about 50°C., more preferably at a temperature of 40-45° C.

The amount of methanesulfonic acid used to effect the deprotection ofthe compound of formula (II) is suitably 2 to 4 equivalents. Forexample, 2.4 equivalents, suitably used at a temperature of between 35°C. and 40° C.; or 3 equivalents, suitably used at ambient temperature.More preferably 2.5 equivalents used at a temperature of 40-45° C.

The reaction is suitably carried out in a solvent, for example, analcohol such as methanol, ethanol, isopropanol, or n-propanol,dichloromethane, acetonitrile, acetone, methyl iso-butyl ketone, DME,ThF, tert-butylmethyl ether, dioxane or ethyl acetate or a mixture ofany of these. The solvent is preferably methanol. Suitably, up to 10equivalents by volume of solvent may be used, e.g. about 4 equivalents.

The compounds of formula (II) may be prepared by the processes describedin U.S. Pat. No. 5,633,262, EP 688772 and PCr/KR99/00099.

The compounds of formula (I) are useful as an intermediates forpreparing quinolone antibacterials particularly those described in U.S.Pat. No. 5,633,262 and EP 688772. Thus according to a further aspect ofthe invention there is provided a process for the production of acompound of formula (III), or a pharmaceutically acceptable salt and/orhydrate thereof:

-   -   wherein R is as defined for formula (I), which comprises        reaction of a compound of formula (I), with a compound of        formula (IV):    -   wherein X is a leaving group, e.g. a halogen atom, preferably        chlorine; and optionally forming a pharmaceutically acceptable        salt and/or hydrate thereof.

Other suitable leaving groups X will be apparent to those skilled in theart.

The reaction of the compounds of formulae (I) and (IV) is preferablyconducted in the presence of a base e.g. triethylamine. The reaction ofthe compounds of formulae (I) and (III) is preferably conducted in asolvent, e.g. acetonitrile, an aqueous solvent such as aqueousacetonitrile or an aqueous alcohol and more preferably water. When wateris used as solvent for this process the resulting compound of formula(III) is of superior quality to that obtained using other solvents. Thisleads to an improvement in the quality of the resulting drug substanceas well as a process that may offer environmental advantages. Furtherdetails regarding the reaction of the compounds of formula (I) and (IV)can be found in U.S. Pat. No. 5,633,262 and EP 688772. The compounds offormula (IV) may be synthesisied as described in U.S. Pat. No. 5,633,262and EP 688772.

The compound of formula (III) produced according to this aspect of theinvention is preferably(R,S)-7(3-aminomethyl-4-syn-methoxyimino-pyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicacid methanesulfonate or a hydrate thereof, preferably thesesquihydrate, as disclosed in WO 98/42705. The methanesulfonate andhydrates thereof may be synthesised from the free acid as described inWO 98/42705 and WO 00/17199.

The compounds of the invention have the advantage that they are stable,i.e. not hygroscopic. They can be isolated from the reaction in higheryield and purity than the corresponding dihydrochloride or free base.The dimesylate salts can be recrystallised if necessary, whereas thecorresponding dihydrochloride or free base has not been successfullyrecrystallised. The dimesylate salts can be used to produce quinoloneantibacterials of high purity and several advantages result from usingthis intermediate. For example, when the resulting drug substance is(R,S)-7-(3-aminomethyl-4-syn-methoxyimino-pyrrolidin-1-yl)1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicacid methanesulfonate or a hydrate thereof, it has improved colour andsignificantly lower levels of high molecular weight impurites comparedto the drug substance produced using the corresponding dihydrochlorideor free base as intermediate.

All publications, including but not limited to patents and patentapplications, cited in this specification are herein incorporated byreference as if each individual publication were specifically andindividually indicated to be incorporated by reference herein as thoughfully set forth.

The invention is illustrated by the following examples. However, itshould be understood that the examples are intended to illustrate butnot in any manner limit the scope of the invention.

EXAMPLE 1

Synthesis of 4-aminomethyl-3-methoxyiminopyrrolidiniumDimethanesulfonate

A solution of 1(N-t-butoxycarbonyl)-4-(t-butoxycarbonylaminomethyl)pyrrolidin-3-methoxime (100 g) in methanol (660 mL) at 15-20° C. undernitrogen was treated with methanesulfonic acid (56.4 mL) over 5 minkeeping the temperature below 30° C. The solution was stirred at 20-25°C. for 16-20 hrs. During this time the product precipitated forming athick suspension. The product was isolated by filtration, washed withmethanol (165 ml) and dried under vacuo at 25° C. to give the titlecompound 84 g (86%).

m.p. 189-193° C.;

m/z: 144 (M+H)⁺;

¹H NMR (400 MHz, d₆-DMSO) δ: 9.27, (2H, brs), 7.95 (3H, brs), 4.01 (1H,d), 3.92 (1H, d), 3.87 (3H, s), 3.69 (1H, m), 3.26 (2H, m), 3.26 (2H,m), 3.15 (1H, m), 3.08 (1H, m), 2.39 (6H, s);

Analysis: C, 28.64%, H, 6.25%, N, 12.46%; C₈H₂₁N₃O₇S₂ requires C,28.65%, H, 6.31%, N, 12.53%.

EXAMPLE 2

Synthesis of 4-aminomethyl-3-methoxyiminopyrrolidiniumDimethanesulfonate

A solution of 1-(N-t-butoxycarbonyl)-4-(t-butoxycarbonylaminomethyl)pyrrolidin-3-methoxime (100 g) in methanol (400 mL) at 20° C. undernitrogen was treated with methanesulfonic acid (47 mL, 70 g, 2.5 equiv)over 15 min keeping the temperature below 25° C. The solution was heatedto 40-45° C. over 30 mins and maintained at this temperature for 4-5hrs. During this time the product precipitated forming a thicksuspension. The crude product was isolated by filtration under nitrogenand washed with methanol (200 mL). The crude product was suspended inmethanol (4 volumes, approx. 360 mL) and heated to reflux for 1 hr.After cooling to 20° C. the suspension was stirred for 1 hour. Theproduct was filtered, washed with methanol (2 volumes, approx. 180 ml)and dried under vacuum at 40° C. to give the title compound 73.8 g(78%). Characterising data were consistent with a standard sample of thetitle compound.

EXAMPLE 3

Synthesis of(R,S)-7-(3-aminomethyl-4-syn-methoxyimino-pyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicAcid

Triethylamine (5.1 ml) was added to7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3carboxylic acid (3.05 g) in water (25 ml) at 15-20° C. and the mixturestirred for 20 min 4-Aminomethyl-3-methoxyimino-pyrrolidiniumdimethanesulfonate (3.86 g) was added, followed by water (5 ml), and themixture stirred at 20-25° C. for 17¾ hours. The resulting product wasfiltered and the cake washed with water (30 ml) followed by ethanol (30ml) and dried under vacuum at 50° C. to give the title compound as awhite solid (4.23 g). (102% as is, 86% on assay). Characterising datawere consistent with a standard sample of the title compound.

EXAMPLE 4

Synthesis of(R,S)-7-(3-aminomethyl-4-syn-methoxyimino-pyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicAcid Methanesulfonate

A solution of methanesulfonic acid (0.33 g, 3.43 mmol) indichloromethane (1 ml) was added to a suspension of(R,S)-7-(3-aminomethyl-4-syn-methoxyiminopyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicacid (1.5 g at 89.9% purity, 3.46 mmol) in a mixture of dichloromethane(23.2 ml) and ethanol (2.7 ml) at 30° C. The mixture was stirred at 30°C. for 3 hours then cooled to 20° C. and filtered. The cake was washedwith dichloromethane (20 ml) and dried at 50° C. under vacuum to givethe title compound (1.71 g) (102% as is, 91% on assay). Characterisingdata were consistent with a standard sample of the title compound.

EXAMPLE 5

Synthesis of(R,S)-7-(3-aminomethyl-4-syn-methoxyimino-pyrrolidin-1-yl)1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicAcid Methanesulfonate Sesquihydrate

(R,S)-7-(3-aminomethyl-4-syn-methoxyiminopyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carboxylicacid methanesulfonate (27.5 g at 91% purity, 51.4 mmol) was stirred in amixture of isopropanol (150 ml) and water (75 ml) and heated until aclear solution was obtained (52° C.). The solution was cooled to 34° C.and seed crystals of(R,S)-7-(3-aminomethyl-4-syn-methoxyiminopyrrolidin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-1,8-naphthyridine-3carboxylic acid methanesulfonate sesquihydrate added. The resultingsuspension was allowed to cool to 25° C. over 1 hour and stirred for 18hours. The slurry was cooled to 0-4° C., stirred for 2 hours, thenfiltered and the cake washed with isopropanol (30 ml). The product wassucked dry for 2 hours and then further dried at 50° C. under vacuum.The dried product was exposed to the atmosphere to give thesesquihydrate, 22.9 g (92%). Characterising data were consistent with astandard sample of the title compound.

1. A compound of formula (I):

wherein R is C₁₋₄ alkyl or C₁₋₄ haloalkyl. 2-10. (canceled).